The invention relates to a catalyst composition comprising a reduced transition metal complex and a cocatalyst.
Catalyst compositions comprising a reduced transition metal complex and a cocatalyst are known from WO-A-96/13529.
In this patent application the reduced transition metal complex of the catalyst composition is represented by the following formula (I): 
wherein the symbols have the following meanings:
M a reduced transition metal selected from group 4, 5 or 6 of the Periodic Table of Elements;
X a multidentate monoanionic ligand represented by the formula: (Arxe2x80x94Rtxe2x80x94)sY(xe2x80x94Rtxe2x80x94DRxe2x80x2n)q;
Y a cyclopentadienyl, amido (xe2x80x94NRxe2x80x2xe2x80x94), or phosphido group (xe2x80x94PRxe2x80x2xe2x80x94), which is bonded to the reduced transition metal M;
R at least one member selected from the group consisting of (i) a connecting group between the Y group and the DRxe2x80x2n group and (ii) a connecting group between the Y group and the Ar group, wherein when the ligand X contains more than one R group, the R groups can be identical to or different from each other;
D an electron-donating hetero atom selected from group 15 or 16 of the Periodic Table of Elements;
Rxe2x80x2 a substituent selected from the group consisting of a hydrogen, hydrocarbon radical and hetero atom-containing moiety, except that Rxe2x80x2 cannot be hydrogen when Rxe2x80x2 is directly bonded to the electron-donating hetero atom D, wherein when the multidentate monoanionic ligand X contains more than one substituent Rxe2x80x2, the substituents Rxe2x80x2 can be identical or different from each other;
Ar an electron-donating aryl group;
L a monoanionic ligand bonded to the reduced transition metal M, wherein at least one L is an electron-donating ligand bonded to M via a metal-carbon bond, and wherein this ligand L is not methyl or benzyl;
K a neutral or anionic ligand bonded to the reduced transition metal M, wherein when the transition metal complex contains more than one ligand K, the ligands K can be identical or different from each other;
m is the number of K ligands, wherein when the K ligand is an anionic ligand m is 0 for M3+, m is 1 for M4+, and m is 2 for M5+, and when K is a neutral ligand m increases by one for each neutral K ligand;
n the number of the Rxe2x80x2 groups bonded to the electron-donating hetero atom D, wherein when D is selected from group 15 of the Periodic Table of Elements n is 2, and when D is selected from group 16 of the Periodic Table of Elements n is 1;
q,s q and s are the number of (xe2x80x94Rtxe2x80x94DRxe2x80x2n) groups and (Arxe2x80x94Rt) groups bonded to group Y, respectively, wherein q+s is an integer not less than 1; and
t the number of R groups connecting each of (i) the Y and Ar groups and (ii) the Y and DRxe2x80x2n, groups, wherein t is selected independently as 0 or 1.
It has now surprisingly been found that when at least one of the monoanionic ligands L in the reduced transition metal complex is bonded to the reduced transition metal M via a covalent metal-carbon bond and additionally this L is capable to non-covalently interact with the metal via one or more functional groups the catalyst composition is more active during olefin polymerisation. A further advantage of the catalyst composition according to the invention is that the reduced transition metal complex is more stable, and can often be obtained as a solid. Therefore the transition metal complex is easier obtained in a pure form and is easier to handle when it is used for olefin polymerisation. When a catalyst composition that is used for olefin polymerization is more active, more polymer per unit of time is produced when using a fixed amount of this catalyst. This is very advantageous in olefin polymerization because polyolefins are produced in large amounts.
Various components of the transition metal complex are discussed below in more detail.
(a) The Transition Metal (M)
The transition metal in the complex is selected from groups 4-6 of the Periodic Table of Elements. As referred to herein, all references to the Periodic Table of Elements mean the version set forth in the new IUPAC notation found on the inside of the cover of the Handbook of Chemistry and Physics, 70th edition, 1989/1990, the complete disclosure of which is incorporated herein by reference.
The transition metal is present in reduced form in the complex, which means that the transition metal is in a reduced oxidation state. As referred to herein, xe2x80x9creduced oxidation statexe2x80x9d means an oxidation state which is greater than zero but lower than the highest possible oxidation state of the metal (for example, the reduced oxidation state is at most M3+ for a transition metal of group 4, at most M4+ for a transition metal of group 5 and at most M5+ for a transition metal of group 6).
(b) The X Ligand
The X ligand is a multidentate monoanionic ligand represented by the formula: (Arxe2x80x94Rtxe2x80x94)sY(xe2x80x94Rtxe2x80x94DRxe2x80x2n)q.
As referred to herein, a multidentate monoanionic ligand is bonded with a covalent bond to the reduced transition metal (M) at one site (the anionic site, Y) and is bonded either (i) with a coordinate bond to the transition metal at one other site (bidentate) or (ii) with a plurality of coordinate bonds at several other sites (tridentate, tetradentate, etc.). Such coordinate bonding can take place, for example, via the D heteroatom or Ar group(s). Examples of tridentate monoanionic ligands include, without limitation, Yxe2x80x94Rtxe2x80x94DRxe2x80x2nxe2x88x921xe2x80x94Rtxe2x80x94DRxe2x80x2n and Y(xe2x80x94Rxe2x80x94DRxe2x80x2n)2. It is noted, however, that heteroatom(s) or aryl substituent(s) can be present on the Y group without coordinately bonding to the reduced transition metal M, so long as at least one coordinate bond is formed between an electron-donating group D or an electron donating Ar group and the reduced transition metal M.
R represents a connecting or bridging group between the DRxe2x80x2n and Y, and/or between the electron-donating aryl (Ar) group and Y. Since R is optional, xe2x80x9ctxe2x80x9d can be zero. The R group is discussed below in paragraph (d) in more detail.
(c) The Y Group
The Y group of the multidentate monoanionic ligand (X) is preferably a cyclopentadienyl, amido (xe2x80x94NRxe2x80x2xe2x80x94), or phosphido (xe2x80x94PRxe2x80x2xe2x80x94) group.
Most preferably, the Y group is a cyclopentadienyl ligand (Cp group). As referred to herein, the term cyclopentadienyl group encompasses substituted cyclopentadienyl groups such as indenyl, fluorenyl, and benzoindenyl groups, and other polycyclic aromatics containing at least one 5-member dienyl ring, so long as at least one of the substituents of the Cp group is an Rtxe2x80x94DRxe2x80x2n group or Rtxe2x80x94Ar group that replaces one of the hydrogens bonded to the five-member ring of the Cp group via an exocyclic substitution.
Examples of a multidentate monoanionic ligand with a Cp group as the Y group (or ligand) include the following (with the (xe2x80x94Rtxe2x80x94DRxe2x80x2n) or (Arxe2x80x94Rtxe2x80x94) substituent on the ring): 
The Y group can also be a hetero cyclopentadienyl group. As referred to herein, a hetero cyclopentadienyl group means a hetero ligand derived from a cyclopentadienyl group, but in which at least one of the atoms defining the five-member ring structure of the cyclopentadienyl is replaced with a hetero atom via an endocyclic substitution. The hetero Cp group also includes at least one Rtxe2x80x94DRxe2x80x2n group or Rtxe2x80x94Ar group that replaces one of the hydrogens bonded to the five-member ring of the Cp group via an exocyclic substitution. As with the Cp group, as referred to herein the hetero Cp group encompasses indenyl, fluorenyl, and benzoindenyl groups, and other polycyclic aromatics containing at least one 5-member dienyl ring, so long as at least one of the substituents of the hetero Cp group is an Rtxe2x80x94DRxe2x80x2n group or Rtxe2x80x94Ar group that replaces one of the hydrogens bonded to the five-member ring of the hetero Cp group via an exocyclic substitution.
The hetero atom can be selected from group 14, 15 or 16 of the Periodic Table of Elements. If there is more than one hetero atom present in the five-member ring, these hetero atoms can be either the same or different from each other. More preferably, the hetero atom(s) is/are selected from group 15, and still more preferably the hetero atom(s) selected is/are phosphorus.
By way of illustration and without limitation, representative hetero ligands of the X group that can be practiced in accordance with the present invention are hetero cyclopentadienyl groups having the following structures, in which the hetero cyclopentadienyl contains one phosphorus atom (i.e., the hetero atom) substituted in the five-member ring: 
It is noted that, generally, the transition metal group M is bonded to the Cp group via an xcex7s bond.
The other Rxe2x80x2 exocyclic substituents (shown in formula (III)) on the ring of the hetero Cp group can be of the same type as those present on the Cp group, as represented in formula (II). As in formula (II), at least one of the exocyclic substituents on the five-member ring of the hetero cyclopentadienyl group of formula (III) is the Rtxe2x80x94DRxe2x80x2n group or the Rtxe2x80x94Ar group.
The numeration of the substitution sites of the indenyl group is in general and in the present description based on the IUPAC Nomenclature of Organic Chemistry 1979, rule A 21.1. The numeration of the substituent sites for indene is shown below. This numeration is analogous for an indenyl group:
The Y group can also be an amido (xe2x80x94NRxe2x80x2xe2x80x94) group or a phosphido (xe2x80x94PRxe2x80x2xe2x80x94) group. In these alternative embodiments, the Y group contains nitrogen (N) or phosphorus (P) and is bonded covalently to the transition metal M as well as to the (optional) R group of the (xe2x80x94Rtxe2x80x94DRxe2x80x2n) or (Arxe2x80x94Rtxe2x80x94) substituent. The Y group can also be a boratabenzene group. In this alternative embodiment, the Y group is a six membered aromatic ring containing 5 carbons and a boron atom. The boratabenzene ring may be substituted.
(d) The R Group
The R group is optional, such that it can be absent from the X group. Where the R group is absent, the DRxe2x80x2n or Ar group is bonded directly to the Y group (that is, the DRxe2x80x2n or Ar group is bonded directly to the Cp, amido, or phosphido group). The presence or absence of an R group between each of the DRxe2x80x2n groups and/or Ar groups is independent.
Where at least one of the R groups is present, each of the R group constitutes the connecting bond between, on the one hand the Y group, and on the other hand the DRxe2x80x2n group or the Ar group. The presence and size of the R group determines the accessibility of the transition metal M relative to the DRxe2x80x2n or Ar group, which gives the desired intramolecular coordination. If the R group (or bridge) is too short or absent, the donor may not coordinate well due to ring tension. The R groups are each selected independently, and can generally be, for example, a hydrocarbon group with 1-20 carbon atoms (e.g., alkylidene, arylidene, aryl alkylidene, etc.). Specific examples of such R groups include, without limitation, methylene, ethylene, propylene, butylene, phenylene, whether or not with a substituted side chain. Preferably, the R group has the following structure:
(xe2x80x94ERxe2x80x22xe2x80x94)pxe2x80x83xe2x80x83(IV)
wherein p is 1, 2, 3, or 4 and wherein E is an element from group 14 of the Periodic Table of the Elements and wherein each E may be the same or different. The Rxe2x80x2 groups of formula (IV) can each be selected independently, and can be the same as the Rxe2x80x2 groups defined below in paragraph (g).
In addition to carbon, the main chain of the R group can also contain silicon or germanium. Examples of such R groups are: dialkyl silylene (xe2x80x94SiRxe2x80x22xe2x80x94), dialkyl germylene (xe2x80x94GeRxe2x80x22xe2x80x94), tetra-alkyl silylene (xe2x80x94SiRxe2x80x22xe2x80x94SiRxe2x80x22xe2x80x94), or tetraalkyl silaethylene (xe2x80x94SiRxe2x80x22CRxe2x80x22xe2x80x94). The alkyl groups in such a group preferably have 1-4 carbon atoms and more preferably are a methyl or ethyl group.
(e) The DRxe2x80x2n Group
This donor group consists of an electron-donating hetero atom D, selected from group 15 or 16 of the Periodic Table of Elements, and one or more substituents Rxe2x80x2 bonded to D. The number (n) of Rxe2x80x2 groups is determined by the nature of the hetero atom D, insofar as n being 2 if D is selected from group 15 and n being 1 if D is selected from group 16. The Rxe2x80x2 substituents bonded to D can each be selected independently, and can be the same as the Rxe2x80x2 groups defined below in paragraph (g), with the exception that the Rxe2x80x2 substituent bonded to D cannot be hydrogen.
The hetero atom D is preferably selected from the group consisting of nitrogen (N), oxygen (O), phosphorus (P) and sulphur (S); more preferably, the hetero atom is nitrogen (N). Preferably, the Rxe2x80x2 group is an alkyl, more preferably an n-alkyl group having 1-20 carbon atoms, and most preferably an n-alkyl having 1-8 carbon atoms. It is further possible for two Rxe2x80x2 groups in the DRxe2x80x2n group to be connected with each other to form a ring-shaped structure (so that the DRxe2x80x2n group can be, for example, a pyrrolidinyl group). The DRxe2x80x2n group can form coordinate bonds with the transition metal M.
(f) The Ar Group
The electron-donating group (or donor) selected can also be an aryl group (C6Rxe2x80x25), such as phenyl, tolyl, xylyl, mesityl, cumenyl, tetramethyl phenyl, pentamethyl phenyl, a polycyclic group such as triphenylmethane, etc. The electron-donating group D of formula (I) cannot, however, be a substituted Cp group, such as an indenyl, benzoindenyl, or fluorenyl group.
The coordination of this Ar group in relation to the transition metal M can vary from xcex71 to xcex76.
(g) The Rxe2x80x2 Group
The Rxe2x80x2 groups may each separately be hydrogen or a hydrocarbon radical with 1-20 carbon atoms (e.g. alkyl, aryl, aryl alkyl and the like). Examples of alkyl groups are methyl, ethyl, propyl, butyl, hexyl and decyl. Examples of aryl groups are phenyl, mesityl, tolyl and cumenyl. Examples of aryl alkyl groups are benzyl, pentamethylbenzyl, xylyl, styryl and trityl. Examples of other Rxe2x80x2 groups are halides, such as chloride, bromide, fluoride and iodide, methoxy, ethoxy and phenoxy.
Also, two adjacent hydrocarbon radicals of the Y group can be connected with each other to define a ring system; therefore the Y group can be an indenyl, a fluorenyl or a benzoindenyl group. The indenyl, fluorenyl, and/or benzoindenyl can contain one or more Rxe2x80x2 groups as substituents. Rxe2x80x2 can also be a substituent which instead of or in addition to carbon and/or hydrogen can comprise one or more hetero atoms of groups 14-16 of the Periodic Table of Elements. Thus, a substituent can be, for example, a Si-containing group, such as Si(CH3)3.
(h) The L Group
The transition metal complex contains one monoanionic ligand L1 bonded to the reduced transition metal center M via a covalent metal-carbon bond and additionally L1 is capable to non-covalently interact with M via one or more functional groups and wherein L1 is not a cyclopentadienyl group, an amido or phosphido group or an unsubstituted benzyl group.
The functional group mentioned above can be one atom, but also a group of atoms connected together. The functional group is preferably an atom of group 17 of the Periodic Table of the Elements or a group containing one or more elements from groups 15, 16 or 17 of the Periodic Table of the Elements. Examples of functional groups are F, Cl, Br, dialkylamino and alkoxy groups.
L1 can for instance be a phenyl group in which at least one of the ortho-positions is substituted with a functional group capable of donating electron density to the transition metal M. L1 can also be a methyl group in which one or more of the alpha-positions is substituted with a functional group capable of donating electron density to the transition metal M.
Examples of methyl groups substituted in one or more of the alpha-positions are benzyl, diphenylmethyl, ethyl, propyl and butyl substituted with a functional group capable of donating electron density to the transition metal M. Preferably at least one of the ortho-positions of a benzyl-group is substituted with a functional group capable of donating electron density to the transition metal M.
Examples of L1 groups are: 2,6-difluorophenyl, 2,4,6-trifluorophenyl, pentafluorophenyl, 2-alkoxyphenyl, 2,6-dialkoxyphenyl, 2,4,6-tri(trifluoromethyl)phenyl, 2,6-di(trifluoromethyl)phenyl, 2-trifluoromethylphenyl, 2-(dialkylamino)benzyl and 2,6-(dialkylamino)phenyl. Most preferably L1 is pentafluorophenyl or 2,6-dimethoxyphenyl because when these L1 groups are used very stable transition metal complexes are formed. L2 is an anionic ligand with the exclusion of a cyclopentadienyl group, an amido or phosphido group. Examples of L2 are a hydrogen atom, a halogen atom, an alkyl aryl or aralkyl group, an alkoxy or aryloxy group. Preferably, L2 is a halogenide or an alkyl or aryl group; more preferably, a Cl group and/or a C1-C4 alkyl or a benzyl group. The L2 group can also be connected to L1 to form a dianionic bidentate ring system. Optionally L2 is equal to L1.
(i) The K Ligand
The K ligand is a neutral or anionic group bonded to the transition metal M. When K is a neutral ligand K may be absent, but when K is monoanionic, the following holds for Km:
m=0 for M3+ and M selected from groups 4, 5 or 6 of the Periodic Table of the Elements,
m=1 for M4+ and M selected from groups 5 or 6 of the Periodic Table of the Elements,
m=2 for M5+ and M selected from group 6 of the Periodic Table of the Elements,
On the other hand, neutral K ligands, which by definition are not anionic, are not subject to the same rule. Therefore, for each neutral K ligand, the value of m (i.e., the number of total K ligands) is one higher than the value stated above for a complex having all monoanionic K ligands.
The K ligand can be a ligand as described above for the L2 group or a Cp group (xe2x80x94C5Rxe2x80x25), an amido group (xe2x80x94NRxe2x80x22) or a phosphido group (xe2x80x94PRxe2x80x22). The K group can also be a neutral ligand such as an ether, an amine, a phosphine, a thioether, among others.
If two K groups are present, the two K groups can be connected with each other via an R group to form a bidentate ring system.
As can also be seen from formula (I), the X group of the complex contains a Y group to which are linked one or more donor groups (the Ar group(s) and/or DRxe2x80x2n group(s)) via, optionally, an R group. The number of donor groups linked to the Y group is at least one and at most the number of substitution sites present on a Y group.
With reference, by way of example, to the structure according to formula (II), at least one substitution site on a Cp group is made by an Rtxe2x80x94Ar group or by an Rtxe2x80x94DRxe2x80x2n group (in which case q+s=1). If all the Rxe2x80x2 groups in formula (II) were Rtxe2x80x94Ar groups, Rtxe2x80x94DRxe2x80x2n groups, or any combination thereof, the value of (q+s) would be 5.
One preferred embodiment of the catalyst composition according to the present invention comprises a transition metal complex in which a bidentate/monoanionic ligand is present and in which the reduced transition metal has been selected from group 4 of the Periodic Table of Elements and has an oxidation state of +3.
In this case, the catalyst composition according to the invention comprises a transition metal complex represented by formula (V): 
where the symbols have the same meaning as described above for formula (I) and where M(III) is a transition metal selected from group 4, 5 or 6 of the Periodic Table of Elements and is in oxidation state 3+. Most preferably M(III) is Ti(III) or Cr(III).
Such a transition metal complex has no anionic K ligands (for an anionic K, m=0 in case of M3+).
It should be pointed out that in WO-A-93/19104, transition metal complexes are described in which a group 4 transition metal in a reduced oxidation state (3+) is present. The complexes described in WO-A-93/19104 have the general formula:
Cpa(ZY)bMLcxe2x80x83xe2x80x83(VI)
The Y group in this formula (VI) is a hetero atom, such as phosphorus, oxygen, sulfur, or nitrogen bonded covalently to the transition metal M (see p. 2 of WO-A-93/19104). This means that the CPa(ZY)b group is of a dianionic nature, and has the anionic charges residing formerly on the Cp and Y groups. Accordingly, the CPa(ZY)b group of formula (VI) contains two covalent bonds: the first being between the 5-member ring of the Cp group and the transition metal M, and the second being between the Y group and the transition metal. By contrast, the X group in the complex according to the present invention is of a monoanionic nature, such that a covalent bond is present between the Y group (e.g., the Cp group) and transition metal, and a coordinate bond can be present between the transition metal M and one or more of the (Arxe2x80x94Rtxe2x80x94) and (xe2x80x94Rtxe2x80x94DRxe2x80x2n) groups. This changes the nature of the transition metal complex and consequently the nature of the catalyst that is active in the polymerization. As referred to herein, a coordinate bond is a bond (e.g., H3Nxe2x80x94BH3) which when broken, yields either (i) two species without net charge and without unpaired electrons (e.g., H3N: and BH3) or (ii) two species with net charge and with unpaired electrons (e.g., H3N.+ and BH3.xe2x88x92). On the other hand, as referred to herein, a covalent bond is a bond (e.g., CH3xe2x80x94CH3) which when broken yields either (i) two species without net charge and with unpaired electrons (e.g., CH3. and CH3.) or (ii) two species with net charges and without unpaired electrons (e.g., CH3+ and CH3:xe2x88x92). A discussion of coordinate and covalent bonding is set forth in Haaland et al. (Angew. Chem Int. Ed. Eng. Vol. 28, 1989, p. 992), the complete disclosure of which is incorporated herein by reference.
The following explanation is proposed, although it is noted that the present invention is in no way limited to this theory.
Referring now more particularly to FIG. 2, the transition metal complexes described in WO-A-93/19104 are ionic after interaction with the co-catalyst. However, the transition metal complex according to WO-A-93/19104 that is active in the polymerization contains an overall neutral charge (on the basis of the assumption that the polymerizing transition metal complex comprises, a M(III) transition metal, one dianionic ligand and one growing monoanionic polymer chain (POL)). By contrast, as shown in FIG. 1, the polymerization active transition metal complex of the catalyst composition according to the present invention is of a cationic nature (on the basis of the assumption that the polymerizing transition metal complexxe2x80x94based on the formula (V) structurexe2x80x94comprises, a M(III) transition metal, one monoanionic bidentate ligand and one growing monoanionic polymer chain (POL)).
Transition metal complexes in which the transition metal is in a reduced oxidation state, but have the following structure:
Cpxe2x80x94M(III)xe2x80x94L2xe2x80x83xe2x80x83(VII)
are generally not active in co-polymerization reactions. It is precisely the presence, in the transition metal complex of the present invention, of the DRxe2x80x2n or Ar group (the donor), optionally bonded to the Y group by means of the R group, that gives a stable transition metal complex suitable for polymerization.
Such an intramolecular donor is to be preferred over an external (intermolecular) donor on account of the fact that the former shows a stronger and more stable coordination with the transition metal complex.
It will be appreciated that the catalyst system may also be formed in situ if the components thereof are added directly to the polymerization reactor system and a solvent or diluent, including liquid monomer, is used in said polymerization reactor.
The catalyst composition of the present invention also contains a co-catalyst. For example, the co-catalyst can be an organometallic compound. The metal of the organometallic compound can be selected from group 1, 2, 12 or 13 of the Periodic Table of Elements. Suitable metals include, for example and without limitation, sodium, lithium, zinc, magnesium, and aluminum, with aluminum being preferred. At least one hydrocarbon radical is bonded directly to the metal to provide a carbon-metal bond. The hydrocarbon group used in such compounds preferably contains 1-30, more preferably 1-10 carbon atoms. Examples of suitable compounds include, without limitation, amyl sodium, butyl lithium, diethyl zinc, butyl magnesium chloride, and dibutyl magnesium. Preference is given to organoaluminium compounds, including, for example and without limitation, the following: trialkyl aluminum compounds, such as triethyl aluminum and tri-isobutyl aluminum; alkyl aluminum hydrides, such as di-isobutyl aluminum hydride; alkylalkoxy organoaluminium compounds; and halogen-containing organoaluminium compounds, such as diethyl aluminum chloride, diisobutyl aluminum chloride, and ethyl aluminum sesquichloride. Preferably, aluminoxanes are selected as the organoaluminium compound.
In addition or as an alternative to the organometallic compounds as the co-catalyst, the catalyst composition of the present invention can include a compound which contains or yields in a reaction with the transition metal complex of the present invention a non-coordinating or poorly coordinating anion. Such compounds have been described for instance in EP-A-426,637, the complete disclosure of which is incorporated herein by reference. Such an anion is bonded sufficiently unstably such that it is replaced by an unsaturated monomer during the co-polymerization. Such compounds are also mentioned in EP-A-277,003 and EP-A-277,004, the complete disclosures of which are incorporated herein by reference. Such a compound preferably contains a triaryl borane or a tetraaryl borate or an aluminum or silicon equivalent thereof. Examples of suitable co-catalyst compounds include, without limitation, the following:
dimethyl anilinium tetrakis (pentafluorophenyl) borate [C6H5N(CH3)2H]+ [B(C6F5)4]xe2x88x92;
dimethyl anilinium bis(7,8-dicarbaundecaborate)-cobaltate (III);
tri(n-butyl)ammonium tetraphenyl borate;
triphenylcarbenium tetrakis (pentafluorophenyl) borate;
dimethylanilinium tetraphenyl borate;
tris(pentafluorophenyl) borane; and
tetrakis(pentafluorophenyl) borate.
As described for instance in EP-A-500,944, the complete disclosure of which is incorporated herein by reference, the reaction product of a halogenated transition metal complex and an organometallic compound, such as for instance triethyl aluminum (TEA), can also be used.
The molar ratio of the co-catalyst relative to the transition metal complex, in case an organometallic compound is selected as the co-catalyst, usually is in a range of from about 1:1 to about 10,000:1, and preferably is in a range of from about 1:1 to about 2,500:1. If a compound containing or yielding a non-coordinating or poorly coordinating anion is selected as co-catalyst, the molar ratio usually is in a range of from about 1:100 to about 1,000:1, and preferably is in a range of from about 1:2 to about 250:1.
As a person skilled in the art would be aware, the transition metal complex as well as the co-catalyst can be present in the catalyst composition as a single component or as a mixture of several components. For instance, a mixture may be desired where there is a need to influence the molecular properties of the polymer, such as molecular weight and in particular molecular weight distribution.
The catalyst composition according to the invention can be used by a method known as such as a catalyst component for the polymerization of an olefin. The olefin envisaged in particular is an olefin chosen from the group comprising xcex1-olefin, internal olefin, cyclic olefin and di-olefin. Mixtures of these can also be used.
The invention relates in particular to a process for the polymerization of an xcex1-olefin. The xcex1-olefin is preferably chosen from the group comprising ethene, propene, butene, pentene, heptene, octene and styrene (substituted or non-substituted), mixtures of which may also be used. More preferably, ethene and/or propene is used as xcex1-olefin. The use of such olefins results in the formation of (semi)crystalline polyethene homo- and copolymers, of high as well as of low density (HDPE, LDPE, LLDPE, etc.), and polypropene, homo- and copolymers (PP and EMPP). The monomers needed for such products and the processes to be used are known to the person skilled in the art.
The process according to the invention is also suitable for the preparation of amorphous or rubber-like copolymers based on ethene and another xcex1-olefin. Propene is preferably used as the other xcex1-olefin, so that EPM rubber is formed. It is also quite possible to use a diene besides ethene and the other xcex1-olefin, so that a so-called EADM rubber is formed, in particular EPDM (ethene propene diene rubber).
The catalyst composition according to the invention can be used supported as well as non-supported. The supported catalysts are used mainly in gas phase and slurry processes. The carrier used may be any carrier known as carrier material for catalysts, for instance SiO2, Al2O3 or MgCl2.
Polymerization of the olefins can be effected in a known manner, in the gas phase as well as in a liquid reaction mediun. In the latter case, both solution and suspension polymerization are suitable, while the quantity of transition metal to be used generally is such that its concentration in the dispersion agent amounts to 10xe2x88x928xe2x88x9210xe2x88x924 mol/l, preferably 10xe2x88x927xe2x88x9210 xe2x88x923 mol/l.
The process according to the invention will hereafter be elucidated with reference to a polyethene preparation known per se, which is representative of the olefin polymerizations meants here. For the preparation of other polymers on the basis of an olefin the reader is expresely referred to the multitde of publications on this subject.
The preparation of polyethene relates to a process for homopolymerization or copolymerization of ethene with one or more xcex1-olefins having 3-12 carbons atoms and optionaly one or more non-conjugated dienes. The xcex1-olefins that are suitable in particular are propene, butene, hexene and octene. Suitable dienes are for instance 1,7-octadiene and 1,9-decadiene. It has been found that the catalyst composition of the present invention is especially suitable for solution or suspension polymerization of ethene.
Any liquid that is inert relative to the catalyst system can be used as dispersion agent in the polymerization. One or more saturated, straight or branched aliphatic hydrocarbons, such as butanes, pentanes, hexanes, heptanes, pentamethyl heptane or mineral oil fractions such as light or regular petrol, naphtha, kerosine or gas oil are suitable for that purpose. Aromatic hydrocarbons, for instance benzene and toluene, can be used, but because of their cost as well as on account of safety considerations, it will be preferred not to use such solvents for production on a technical scale. In polymerization processes on a technical scale, it is preferred therefore to use as solvent the low-priced aliphatic hydrocarbons or mixtures thereof, as marketed by the petrochemical industry. If an aliphatic hydrocarbon is used as solvent, the solvent may yet contain minor quantities of aromatic hydrocarbon, for instance toluene. Thus, if for instance methyl aluminoxane (MAO) is used as co-catalyst, toluene can be used as solvent in order to supply the MAO in dissolved form to the polymerization reactor. Drying or purification is desirable if such solvents are used; this can be done without problems by the average person skilled in the art.
Such a solution polymerization is preferably carried out at temperatures between 150xc2x0 C. and 250xc2x0 C.; in general, a suspension polymerization takes place at lower temperatures, preferably below 100xc2x0 C.
The polymer solution resulting from the polymerization can be worked up by a method known per se. In general the catalyst is de-activated at some point during the processing of the polymer. The de-activation is also effected in a manner known per se, e.g. by means of water or an alcohol. Removal of the catalyst residues can mostly be omitted because the quantity of catalyst in the polymer, in particular the content of halogen and transition metal is very low now owing to the use of the catalyst system according to the invention.
Polymerization can be effected at atmospheric pressure, but also at an elevated pressure of up to 500 MPa, continuously or discontinuously. If the polymerization is carried out under pressure the yield of polymer can be increased additionally, resulting in an even lower catalyst residue content. Preferably, the polymerization is performed at pressures between 0.1 and 25 MPa. Higher pressures, of 100 MPa and upwards, can be applied if the polymerization is carried out in so-called high-pressure reactors. In such a high-pressure process the catalyst according to the present invention can also be used with good results.
The polymerization can also be performed in several steps, in series as well as in parallel. If required, the catalyst composition, temperature, hydrogen concentration, pressure, residence time, etc. may be varied from step to step. In this way it is also possible to obtain products with a wide molecular weight distribution.
The invention also relates to a polyolefin that can be obtained by means of a polymerization process with utilization of the catalyst composition according to the invention.